Dental instruments commonly include an air turbine driven by compressed air from a drive line. Such instruments include high and low speed turbine handpieces and scaling instruments, and all forms are referred to herein as turbine handpieces. The air drive line is routed within a flexible hose having an end fitting for removable attachment of the turbine handpiece. Also contained within the flexible hose are an exhaust line for returning the drive air after it has served its function in driving the turbine, a coolant line for removing excess heat from the dental work site, and in the case of high speed turbine handpieces a chip air line which mixes the compressed air with the coolant to generate a spray. During operation of dental turbine handpieces some debris from the mouth such as saliva, cuttings, coolant and pathogens, enters the turbine of the handpiece. The pressurized air that drives the turbine is not capable of flushing out this debris and indeed the debris may not even be fully flushed out during sterilization by autoclaving which normally is carried out on the handpiece after each use on a patient.
Dental turbine handpieces also require periodic lubrication. For this purpose the conventional practice is to remove the handpiece from the hose end fitting and connect it to an aerosol container of a lubricant which is typically of a petroleum base such as naphtha. A few bursts from the container serve to lubricate the moving parts of the turbine. The efficiency of the aerosol container decreases of course as its propellant is exhausted and it is by no means ideal that petroleum-based lubricant later enters the mouth of the patient, but those disadvantages have been tolerated.
It is the principal purpose of the present invention to provide a method by which the turbine of a dental handpiece may be disinfected after each use and flushed of all dental debris and simultaneously lubricated without necessitating the use of separate lubricant containers. This is to be achieved by forcing a pressurized solution of a disinfectant-lubricant through the air drive line to the turbine of the handpiece when it is not in operation on a patient, thus flushing dental debris through the exhaust line and effectively lubricating the moving parts of the turbine. Petroleum based lubricants are to be avoided.
My U.S. Pat. No. 4,668,190 describes apparatus for injecting a liquid solution into a dental water-injection system and certain of the components of that apparatus are useful in practicing the method of the present invention. I also describe in my U.S. Pat. No. 4,695,255 a method of lubricating human hard tissue during cutting by directing against that hard tissue a flow of solution which includes glycerin as a lubricating agent, and glycerin is the preferred lubricant in the practice of the present invention. Neither of these prior art references discloses any method of disinfecting and lubricating a dental turbine handpiece.
Elsewhere in the prior art it is known to deliver a liquid solution to a dental handpiece. For example U.S. Pat. No. 3,987,550 teaches the introduction of a prophylaxis material (a cleaning agent) through a slow speed handpiece and U.S. Pat. Nos. 3,949,753, 4,193,196 and 5,044,952 disclose other similar methods and apparatus. In each of them a solution is transmitted one way or the other through a dental instrument into the patient's mouth. None of those references, however, teaches the introduction of any solution through an air drive line of a dental turbine handpiece when it is not in operation, nor do they teach simultaneous disinfecting and lubricating of the turbine by the solution introduced through the air drive line.
U.S. Pat. No. 4,990,087 is also relevant because it discloses a method of lubricating, disinfecting and flushing a dental handpiece. However three distinct fluids are employed in that method. First a liquid lubricant from one bottle is passed through the air drive line to the turbine, then a liquid disinfectant from another bottle is passed through the coolant line but not the turbine air drive line and finally compressed air is injected for flushing. The method is deficient in that the disinfectant does not reach contaminating debris within the turbine or the chip air line. Moreover this method concludes with an air purging step which removes both excess disinfectant and lubricant. If autoclaving is carried out subsequently this is a disadvantage because a residue of disinfectant continues to function effectively during autoclaving. And a residue of lubricant is obviously desirable to be effective later during operation of the moving parts of the turbine.